im about to get a used aqueon evolve 4gallon. it has a builtin filter with a place where you can hide your heater. it looks like theres no cords at all. you should try craigslist once in a while to find deals. isaw a fluval edge 6gallon looking almost new with replaced lights and heater for 75. you could probably offer 20%less than their asking

I have that same tank! But make sure the filter flow isnt too strong for you betta. Mine was so i came up with a solution. I poked a couples holes in the pump tubing and covered the output nozzle with a piece of pantyhose with a rubberband. You could also use a filter sponge.